Come estrarre determinati blocchi da xml in java?

Ho il seguente file xml.Come estrarre determinati blocchi da xml in java?

<?xml version="1.0" encoding="UTF-8"?> 
<databaseChangeLog> 
    <changeSet author="debdipta.h (generated)" id="1442927616936-399"> 
     <createTable tableName="SI_FORWARDING_EVENT_HISTORY_AU"> 
     <column name="FORWARDING_ID_O" type="NUMBER" /> 
     <column name="FORWARDING_ID_N" type="NUMBER" /> 
     <column name="ASSIGNMENT_ID_O" type="NUMBER" /> 
     <column name="ASSIGNMENT_ID_N" type="NUMBER" /> 
     <column name="PROCESS_INSTANCE_ID_O" type="NUMBER" /> 
     <column name="PROCESS_INSTANCE_ID_N" type="NUMBER" /> 
     <column name="ORIGINAL_USER_ID_O" type="NUMBER" /> 
     <column name="ORIGINAL_USER_ID_N" type="NUMBER" /> 
     <column name="FORWARD_FROM_USER_O" type="NUMBER" /> 
     <column name="FORWARD_FROM_USER_N" type="NUMBER" /> 
     <column name="FORWARD_TO_USER_O" type="NUMBER" /> 
     <column name="FORWARD_TO_USER_N" type="NUMBER" /> 
     <column name="COMMENTS_O" type="VARCHAR2(4000 CHAR)" /> 
     <column name="COMMENTS_N" type="VARCHAR2(4000 CHAR)" /> 
     <column name="XML_O" type="VARCHAR2(4000 CHAR)" /> 
     <column name="XML_N" type="VARCHAR2(4000 CHAR)" /> 
     <column name="CREATED_BY_O" type="NUMBER" /> 
     <column name="CREATED_BY_N" type="NUMBER" /> 
     <column name="CREATION_DATE_O" type="date" /> 
     <column name="CREATION_DATE_N" type="date" /> 
     <column name="AUDIT_TRAIL_REASON" type="VARCHAR2(1000 CHAR)" /> 
     <column name="TRANSACTION_TYPE" type="VARCHAR2(100 CHAR)" /> 
     </createTable> 
    </changeSet> 

    <changeSet author="deb.h" id="4588999797"> 
     <createView /> 
    </changeSet> 

    <changeSet author="deb.h" id="4588999797"> 
     <createTable /> 
    </changeSet> 

    <changeSet author="deb.h" id="4588999797"> 
     <createView /> 
    </changeSet> 
</databaseChangeLog>

Voglio estrarre i blocchi solo CreateTable essere estratti a qualche altro file XML utilizzando XPath. Il risultato dovrebbe essere simile:

<databaseChangeLog> 
<changeSet author="debdipta.h (generated)" id="1442927616936-399"> 
     <createTable tableName="SI_FORWARDING_EVENT_HISTORY_AU"> 
      <column name="FORWARDING_ID_O" type="NUMBER"/> 
      <column name="FORWARDING_ID_N" type="NUMBER"/> 
      <column name="ASSIGNMENT_ID_O" type="NUMBER"/> 
      <column name="ASSIGNMENT_ID_N" type="NUMBER"/> 
      <column name="PROCESS_INSTANCE_ID_O" type="NUMBER"/> 
      <column name="PROCESS_INSTANCE_ID_N" type="NUMBER"/> 
      <column name="ORIGINAL_USER_ID_O" type="NUMBER"/> 
      <column name="ORIGINAL_USER_ID_N" type="NUMBER"/> 
      <column name="FORWARD_FROM_USER_O" type="NUMBER"/> 
      <column name="FORWARD_FROM_USER_N" type="NUMBER"/> 
      <column name="FORWARD_TO_USER_O" type="NUMBER"/> 
      <column name="FORWARD_TO_USER_N" type="NUMBER"/> 
      <column name="COMMENTS_O" type="VARCHAR2(4000 CHAR)"/> 
      <column name="COMMENTS_N" type="VARCHAR2(4000 CHAR)"/> 
      <column name="XML_O" type="VARCHAR2(4000 CHAR)"/> 
      <column name="XML_N" type="VARCHAR2(4000 CHAR)"/> 
      <column name="CREATED_BY_O" type="NUMBER"/> 
      <column name="CREATED_BY_N" type="NUMBER"/> 
      <column name="CREATION_DATE_O" type="date"/> 
      <column name="CREATION_DATE_N" type="date"/> 
      <column name="AUDIT_TRAIL_REASON" type="VARCHAR2(1000 CHAR)"/> 
      <column name="TRANSACTION_TYPE" type="VARCHAR2(100 CHAR)"/> 
     </createTable> 
</changeSet> 

<changeSet author="deb.h" id="4588999797"> 
     <createTable></createTable> 
</changeSet> 
</databaseChangeLog>

Il codice che ho fatto ancora oggi è la seguente:

public class extractXML { 
    public static void main(String[] args)throws Exception{ 
     //String test=readXMLasString.convert("E:\\db.borilog.xml"); 
     DocumentBuilderFactory dbf=DocumentBuilderFactory.newInstance(); 
     DocumentBuilder db=dbf.newDocumentBuilder(); 
     Document doc=db.parse(new FileInputStream("E:\\db.borilog.xml")); 
     XPath xpath=XPathFactory.newInstance().newXPath(); 
     Node res=(Node) xpath.evaluate("databaseChangeLog/changeSet",doc,XPathConstants.NODE); 
     System.out.println(NodeToString(res)); 
    } 

public static String NodeToString(Node node)throws TransformerException{ 
    StringWriter buf=new StringWriter(); 
    Transformer xform=TransformerFactory.newInstance().newTransformer(); 
    xform.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes"); 
    xform.transform(new DOMSource(node),new StreamResult(buf)); 
    return(buf.toString()); 


} 
}

Non sto undrstanding come scorrere l'XPath ed estrarre i blocchi necessari.

fonte

2015-10-20 Debdipta Halder

Eventuali duplicati di [Come leggere XML utilizzando XPath in Java] (http://stackoverflow.com/questions/2811001/ how-to-read-xml-using-xpath-in-java) –

Ciò restituirebbe blocchi a tutti i blocchi createTable.

//changeSet[createTable]

/databaseChangeLog/changeSet[createTable]

Qui si chiede di restituire blocchi changeset in cui è presente CreateTable.

Risultato

<changeSet author="debdipta.h (generated)" id="1442927616936-399"> 
    <createTable tableName="SI_FORWARDING_EVENT_HISTORY_AU"> 
    <column name="FORWARDING_ID_O" type="NUMBER" /> 
    <column name="FORWARDING_ID_N" type="NUMBER" /> 
    <column name="ASSIGNMENT_ID_O" type="NUMBER" /> 
    <column name="ASSIGNMENT_ID_N" type="NUMBER" /> 
    <column name="PROCESS_INSTANCE_ID_O" type="NUMBER" /> 
    <column name="PROCESS_INSTANCE_ID_N" type="NUMBER" /> 
    <column name="ORIGINAL_USER_ID_O" type="NUMBER" /> 
    <column name="ORIGINAL_USER_ID_N" type="NUMBER" /> 
    <column name="FORWARD_FROM_USER_O" type="NUMBER" /> 
    <column name="FORWARD_FROM_USER_N" type="NUMBER" /> 
    <column name="FORWARD_TO_USER_O" type="NUMBER" /> 
    <column name="FORWARD_TO_USER_N" type="NUMBER" /> 
    <column name="COMMENTS_O" type="VARCHAR2(4000 CHAR)" /> 
    <column name="COMMENTS_N" type="VARCHAR2(4000 CHAR)" /> 
    <column name="XML_O" type="VARCHAR2(4000 CHAR)" /> 
    <column name="XML_N" type="VARCHAR2(4000 CHAR)" /> 
    <column name="CREATED_BY_O" type="NUMBER" /> 
    <column name="CREATED_BY_N" type="NUMBER" /> 
    <column name="CREATION_DATE_O" type="date" /> 
    <column name="CREATION_DATE_N" type="date" /> 
    <column name="AUDIT_TRAIL_REASON" type="VARCHAR2(1000 CHAR)" /> 
    <column name="TRANSACTION_TYPE" type="VARCHAR2(100 CHAR)" /> 
    </createTable> 
</changeSet> 
<changeSet author="deb.h" id="4588999797"> 
    <createTable /> 
</changeSet>

fonte

2015-10-20 12:13:44

Restituisce solo un blocco createTable. –

Sta trovando la prima istanza della createTable che ha ottenuto. –

è perché hai un problema nel tuo XML. Ci sono 2 cambi chiusi in esso vanno uno per uno. –

È necessario utilizzare NodeList:

NodeList nodeList = (NodeList)xpath.evaluate("//changeSet[createTable]",doc,XPathConstants.NODE); 
String[] results = new String[nodeList.getLength()]; 
for (int index = 0; index < nodeList.getLength(); index++) { 
    Node node = nodeList.item(index); 
    String nodeAsString = NodeToString(node); 
    results[index] = nodeAsString; 
}

fonte

2015-10-20 14:14:51

Sì, finalmente risolto il problema. grazie per l'aiuto. –

Come estrarre determinati blocchi da xml in java?

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